Peh, WCG

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Title Radiological conference. Medullary sponge kidneyAuthor(s) Peh, WCGCitation Hong Kong Practitioner, 1999, v. 21 n. 1, p. 30-33Issued Date 1999URL http://hdl.handle.net/10722/44674Rights Creative Commons: Attribution 3.0 Hong Kong License™A 22-year-old man presented with bilateral loin pain. He passed out a small stone on the day of his intravenousurogram (IVU). Preliminary radiograph (Figure 1) and IVU (Figure 2) were performed.Figure 1: Frontal radiograph coned to the kidney Figure 2: Ten-minute IVU film (frontal projection)Answeronpage 31What Is the diagnosis?a) Medullary sponge kidneyb) Tuberculosisc) Renal cell carcinomad) Renal papillary necrosise) Enteric hyperoxaluriaThis radiology case was prepared by:30Professor W.C.G. Peh,Department of Diagnostic Radiology,The University of Hong Kong,Queen Mary Hospital.Hong Kong Practitioner 21 (1) January 1999Answer:a) Medullary sponge kidneyRadiological findingsOn the p re l iminary radiograph, m u l t i p l e smal lrounded ca lc i f i ca t ions are projected over both renaloutlines. The calcifications are clustered, producing a"bunch of grapes" appearance. These calcifications aretypical of parenchymal calcifications or nephrocalcinosis(Figure 3). IVU shows s l ight enlargement of bothkidneys. The medullary papillae are swollen, and containm u l t i p l e contrast-opacified cysts and streaks. Thec a l c i f i c a t i o n s l i e w i t h i n these o p a c i f i e d areas.Appearances are typical of medullary sponge kidney.Figure 3: Same radiograph as Figure 1 with theaddition of arrows. Multiple clusteredcalcifications are seen, resembling"bunches of grapes" (arrows)DiscussionMedullary sponge kidney is a congenital disease inwhich the collecting ducts are abnormally dilated. Thisproduces a sponge-like appearance in the papi l la rymedulla. Numerous cysts, varying in size from 1 to 3 mmin diameter, communicate with these dilated tubules. Thedense streaks of contrast in the medullary pyramids givea "bunch of flowers" appearance. Calculi are present in80% of the cysts, presumably due to urinary pooling.1-3Figure 4: Same radiograph as Figure 2 with theaddition of arrows. Both pelvicalycealsystems are opacified by contrast. Tinycysts (arrowheads) and streaks (smallarrows) are present within the enlargedmedullary papillaeThis disease may affect the whole or part of one orboth kidneys. Unilateral involvement is present in 25%of cases. It typically affects young to middle-aged adults,and has an incidence of 0.5%. Uncomplicated disease isusually clinically silent. Secondary infection or passageof calculi, such as in our patient, may produce symptoms.Obstruction by calculi or repeated infection may lead toimpaired renal function. Medullary sponge kidney maybe associated with Ehlers-Danlos syndrome, parathyroidadenoma or Caroli disease.1-3TuberculosisThe earliest sign of tuberculosis of the kidney ispapil lary erosion, which is seen as a central cavity onIVU. Cavitation may spread to involve the rest of therenal parenchyma. Fibrosis causes calyceal neck stenosis,producing obstruction of the calyces. Tuberculosis ischaracterised by multiple sites of involvement, i.e. thek idneys , ureters and bladder. Calci f icat ion may benodular, curvilinear or amorphous, and usually involvesone kidney or part of one kidney. If renal tuberculosisis untreated, the whole kidney may become completelycalcified, producing the so-called autonephrectomy.1 - 2This d i agnos i s can be exc luded in our p a t i e n t onradiological grounds.(Continued on page 33)31Hong Kong Practitioner 21 (1) January 1999RADIOLOGICAL CONFERENCERenal cell carcinomaCalc i f ica t ion is seen in only 6% of renal cellcarc inomas . Ca l c i f i c a t i on , i f present , is u s u a l l yamorphous or irregular. Only one kidney or part of thekidney involved by the tumour is calcificed. On IVU, thepelvicalyceal system may be invaded and amputated bya mass lesion. The patient may present with the classicalclinical triad of flank mass, pain and haematuria.1-2 Theseclinical and imaging features were not present in ourpatient.Renal papillary necrosisRenal papillary necrosis may be caused by a varietyof disorders, the most important of which are diabetes,analgesics and sickle cell anaemia. The kidneys areusually small with smooth outlines. On IVU, there maybe papillary swelling in the early stage of the disease.Later, papillary slough results in fissuring and cavitationwhich communicates with the calyces. Sloughing maygive the calyces an irregular dilated appearance. Theshed papillae may cause ureteric obstruct ion and ifbilateral, acute renal failure. Infection and dehydrationmay occur. In the late stage, calcification of necroticpapillae may occur. This disease is bilateral in 80% withmultiple papillae affected.1-2 In our patient, this diagnosiscan be excluded clinically and by imaging.Enteric hyperoxaluriaThis is a rare condition due to a disturbance of bileacid metabolism. It occurs in patients with small boweldisease, such as Crohn's disease or surgical resection.Hyperoxaluria produces pure calcium oxalate calculi.The pattern of calcif icat ions seen in our patient isdifferent from that of renal calculi. On IVU, calculi arelocated in the pelvicalyceal systems, not within themedullary papillae. •ReferencesSherwood T. Uroradiology. Blackwell Scientific, Oxford, 1980;pp87-210.Chapman S, Nakielny R. Aids to Radiological Differential Diagnosis. 3rded. WB Saunders, London. l995;pp294-297.Dahnert W. Radiology Review Manual. 3rd ed. Baltimore: Will iams &Wilkins, 1996;pp576-577.33

Radiological conference. Medullary sponge kidney

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